1. Field of the Invention
Aspects of the present invention relate to an organic electrolytic solution including a glycidyl ether compound and a lithium battery employing the same. More particularly, aspects of the present invention relate to an organic electrolytic solution including a glycidyl ether compound capable of effectively inhibiting side reactions and a lithium battery capable of improving a battery charge/discharge characteristics by employing the organic electrolytic solution.
2. Description of the Related Art
As portable electronic devices such as video cameras, cellular phones, notebook computers, etc., become more lightweight and have increasingly improved performance, research into batteries used as power supplies for such portable devices is being conducted. In particular, rechargeable lithium secondary batteries are being actively researched, since they have three times the energy density per unit weight compared to conventional lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, etc., and can be rapidly charged. In general, since a lithium battery is generally driven at a high operating voltage, a conventional aqueous electrolyte solution cannot be used. This is because lithium contained in an anode and an aqueous solution vigorously react with each other. Thus, an organic electrolytic solution in which a lithium salt is dissolved in an organic solvent is generally used as the electrolyte in a lithium battery. Such organic solvents should generally have high ionic conductivity, a high dielectric constant and low viscosity. However, since it is difficult to obtain a single organic solvent satisfying all these requirements, a mixed solvent may be used that includes, for example, an organic solvent with a high dielectric constant and an organic solvent with a low viscosity.
When using a carbonate-based polar nonaqueous solvent, carbon contained in an anode and an electrolyte in the lithium secondary battery react with each other during the initial charging, and thus, an excess amount of electric charge is used. In such an irreversible reaction, a passivation layer, such as a solid electrolyte interface (SEI) film, is formed on the surface of the negative electrode. The SEI film enables the battery to be stably charged and discharged without further decomposition of the electrolyte solution (J. Power Sources, 51(1994), 79-104). The SEI film also acts as an ion tunnel through which only lithium ions pass. Generally, organic solvents solvate lithium ions. Thus, cointercalation of an organic solvent, which solvates the lithium ions and moves with the lithium ions into a carbon anode during charging and discharging of the battery, generally occurs. However, an SEI film as described above only allows lithium ions to pass and prevents cointercalation of an organic solvent, thereby preventing a breakdown of the anode structure which is caused by cointercalation of the organic solvent during charging and discharging of the battery. However, the SEI film gradually cracks due to swelling and shrinking of an active material caused by repeated charging and discharging and becomes separated from the surface of the electrode. Thereafter, since the electrolyte directly contacts the active material, the electrolyte becomes continuously decomposed. The cracks of the SEI film develop as a result of charging and discharging of the battery and deteriorate the active material. Particularly, if the active material includes a metal such as silicon, a large variation of the active material volume increases the deterioration of the active material. In addition, repeated swelling and shrinking of the active material volume induces agglomeration of silicon particles.
Accordingly, in order to solve the problems of the conventional art, improvement of charge/discharge characteristics of batteries is still desired by preventing direct contact between a metal active material and an electrolyte without decreasing the ionic conductivity of lithium ions.